1. Field of the Invention
The present invention relates in particular to a power conversion apparatus for vehicle use which is adapted to be supplied to a traction motor, a motor for power generation, etc., used in a hybrid vehicle, an electric vehicle or the like.
2. Description of the Related Art
In the past, as a drive control apparatus of an electric rotating machine which is an electric power source, there has been used a power conversion apparatus that is provided with a semiconductor module and a control board for controlling the driving, protection, etc., of a semiconductor switching device which is a component element of the semiconductor module.
The power conversion apparatus includes an inverter that serves to convert a direct current power into an alternating current power, and a DC-DC converter that serves to convert a direct current power of a certain voltage into another direct current power of a different voltage, wherein a simple inverter, a simple DC-DC converter, a combined unit of these inverter and converter, etc., have been put into practical use.
As such a conventional power conversion apparatus, there has been known one in which a plurality of semiconductor modules each having a semiconductor chip received in an envelope composed of a base and an insulating package are arranged on a common heat sink with its top surface of a flat shape (see a first prior art reference Japanese patent application laid-open No. 2001-168278 (paragraph Nos. 0018, 0027, 0028 and 0034)).
Each semiconductor module of this first prior art reference is constructed such that a semiconductor chip of an insulated gate bipolar transistor (IGBT) and a diode are connected in parallel to each other, wherein a plurality of main terminals (large current conducting terminals) each having a through hole for a conductor mounting bolt formed therethrough are arranged in parallel to the base so as to protrude outwardly of the package.
In addition, signal terminals (gate terminals) are arranged on the opposite side of the main terminals across the package. Each semiconductor module is fixedly secured to the heat sink by means of mounting bolts which pass through mounting holes formed in four corners of the base.
Moreover, six semiconductor modules are used as the semiconductor modules so as to form a three-phase inverter which acts as a power conversion apparatus, and mounting bolts are caused to penetrate through the corresponding main terminals of each semiconductor module, which are then electrically joined to conductors (bus bars), thereby forming wiring for an inverter main circuit.
Further, as another conventional power conversion apparatus, there has been know one in which a plurality of semiconductor modules each have a semiconductor chip received therein, similar to the semiconductor modules in the above-mentioned first prior art reference, wherein main terminals and signal terminals are arranged so as to protrude from an insulating package of a module body of each semiconductor module in opposite directions different substantially 180 degrees from each other, with a pair of radiator plates being exposed to the opposite sides, respectively, of a principal plane (from which no terminals protrude and which has a relatively large area) of the package (see a second prior art reference Japanese patent application laid-open No. 2005-73374 (paragraph Nos. 0011 and 0017-0024)).
A plurality of semiconductor modules in this second prior art reference are held side by side between a pair of refrigerant tubes which function as heat sinks. The main terminals protruded from the package of each semiconductor module are electrically joined to conductors (bus bars) that are arranged on a plane substantially perpendicular to the principal plane of the package, and have wiring formed thereon as a main circuit of the power conversion apparatus.
In addition, at a side at which the signal terminals protrude, a control board is arranged substantially at right angles with respect to the principal plane of the package, and control circuit components on the control board and the signal terminals of the semiconductor modules are electrically connected with each other by inserting the signal terminals into a plurality of connection holes formed in the control board.
However, in the power conversion apparatus of the first prior art reference, as shown in FIG. 5 to be described later, the plurality of semiconductor modules are arranged on the same plane, so the outside size of the power conversion apparatus is increased, as a result of which there has been a problem that the cost and weight of the power conversion apparatus as a product increase.
That is, in the first prior art reference, the respective semiconductor modules are arranged on the common heat sink in a planar manner, so the heat sink is made larger in size in accordance with the number of the semiconductor modules to be used.
In addition, since the semiconductor modules are fixedly secured to the heat sink by means of the mounting bolts passing through the mounting holes formed in the four corners of the base, it is necessary to secure a space for arranging the mounting holes, as a result of which the installation project area of the semiconductor modules themselves spreads or increases.
Further, the heat sink is composed of a metallic material due to its cooling capability and its structural strength requirement, so the weight of the heat sink increases to a remarkable extent due to the increased size of the heat sink.
In addition, in the power conversion apparatus of the second prior art reference, it is formed such that each of the semiconductor modules is held between and by a pair of refrigerant tubes (or heat sinks), and the conductors (bus bars) are arranged at the side at which the main terminals of the semiconductor modules are protruded, and the control board is arranged at the side at which the signal terminals are protruded.
Since the plurality of semiconductor modules and heat sinks are stacked or laminated to form a three dimensional shape, the project areas of the semiconductor modules and the heat sinks can be made smaller as compared with those in the conventional power conversion apparatus disclosed in the first prior art reference. Thus, in cases where the power conversion apparatus has high output capacity, it can be achieved by arranging a multitude of laminated units of semiconductor modules and heat sinks in a lamination direction.
However, in the power conversion apparatus of the second prior art reference, wirings of the conductors are arranged at one side and the other side of the semiconductor modules in a collected manner, and the signal terminals are also arranged at the other side of the semiconductor modules in a collected manner, as shown in FIGS. 7(a) and 7(b) to be described later, so there have been problems that it is difficult to adjust the proportions of individual installation volumes or spaces required by the main terminals, the conductor wiring parts, the semiconductor modules, the heat sinks, and the control board, and that the assembly efficiency thereof is low.
In particular, in cases where extremely thin type heat sinks are applied as the heat sinks, the distance between adjacent signal terminals projected from adjacent semiconductor modules located in a line on opposite sides of each heat sink becomes shorter, but on the other hand, the size of the control board components remains unchanged, and the area of the control board can not be reduced, so the volume enveloping the whole of the main terminals, the conductor wiring parts, the semiconductor modules, the heat sinks, and the control board is not necessarily reduced.
In addition, in cases where a multitude of semiconductor modules and heat sinks are stacked or laminated in order to obtain a power conversion apparatus of large-capacity output, the difference between the length in the lamination direction and the long side length of the rectangular control board becomes shorter, so the above-mentioned problem in connection with the adjustment of the proportions of the installation volumes or spaces can be alleviated to some extent.
However, in cases where the output of the power conversion apparatus may be small and the number of laminations of the semiconductor modules and heat sinks may also be small, i.e., for the power conversion apparatus which should be essentially achieved with a small size, the above-mentioned problem is not still solved.
In addition, in the second prior art reference, the arrangement of the signal terminals of the semiconductor modules becomes substantially perpendicular to the magnetic field generated in accordance with the operation of the semiconductor modules, so it is considered that the magnetic flux generated from the semiconductor modules interlinks with the signal terminals, thereby causing a malfunction in the control of the semiconductor modules. Therefore, the implementation of noise countermeasures is needed, which results in problems such as an increase in the number of component parts required, a rise in cost, etc.
In order to make the power conversion apparatus small-sized, it is desirable that each of the heat sinks, the semiconductor modules and the control board be made small in size and light in weight.
However, the miniaturization of the apparatus can not be achieved only due to the reduction in the size thereof.
As an example of restrictions on this, it is necessary to secure an insulation distance in a portion to which a high voltage is applied to generate a high potential difference.
In order for the power conversion apparatus to operate normally, it is necessary to prevent a leakage of current and a dielectric breakdown, and technical specifications to be applied are prescribed, for example, by International Standard IEC 60950 (Information technology equipment-safety), Japanese Industrial Standards JIS C5014 (Multilayer Printed Wiring Boards), JIS D5305-3 (Electric road vehicles-Safety specifications-part 3: Protection of persons against electric hazards), etc.
Based on these, in cases where there is a potential difference between the electrodes of electrically conductive patterns and/or electronic parts which are exposed outside on the control board, it is necessary to arrange them at a predetermined distance therebetween, i.e., to provide a predetermined creepage distance or a predetermined spatial clearance.
For example, the brocking voltage of the semiconductor modules is selected according to the operating voltage of the power conversion apparatus, and there are 1,200 V, 1,800 V, etc., for the brocking voltage. In cases where the insulation distance of the control board is designed based on the voltage value of this brocking voltage, the creepage distance at a potential difference of 1,200 V amounts to about 6 mm, and that at a potential difference of 1,800 V also amounts to about 9 mm, as shown in FIG. 29.
With respect to this, in the power conversion apparatus of the second prior art reference, even if the heat sinks and the semiconductor modules can be formed to be thin in thickness, as shown in FIG. 7(b) to be described later, the signal terminals protruded from the semiconductor modules have a potential difference according to the operating voltage range of the power conversion apparatus, so the electrically conductive patterns and the electronic parts have to be arranged in such a manner that the electric conductive patterns on the control board, the electrodes of the electronic parts, electrically connected to the signal terminals and the like can secure a creepage distance corresponding to the potential difference.
Accordingly, even in cases where thin heat sinks are applied, the volume enveloping the entire power conversion apparatus is not reduced to a sufficient extent, and the signal terminals protruded from the semiconductor modules have to be bent so as to secure a creepage distance on the control board, thus giving rise to problems such as the addition of processing, the rise of costs, etc.
Further, in the second prior art reference, the fixed connection of the control board with the semiconductor modules and the heat sinks requires the fixing thereof by means of a structural member of high rigid, separately from the connection thereof by the signal terminals of low rigidity, and hence a holding structural member is provided which has a strength capable of suppressing vibration of the control board, as a result of which there are also problems such as an increase in the weight of the apparatus and a deterioration of assembling workability.